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CLAUDE September 22, 2026

Claude Opus 5.5 Released: 40% Cheaper, Matches Fable 5.1 [Sept 22]

WHAT CHANGED

Anthropic launched Claude Opus 5.5 on September 22, 2026 — the first model in the new Claude 5.5 family. It matches Claude Fable 5.1 performance on most work at 40% lower cost than Opus 5. Pricing: $4 per million input tokens, $20 per million output tokens, $0.20 per million cache reads. 1M-token context window, 128K max output, always-on adaptive thinking. Available on the Claude API, Amazon Bedrock, Claude Platform on AWS, Google Cloud, and Microsoft Foundry.

WHY IT MATTERS

Opus 5.5 collapses the price-performance frontier. Frontier-level capability (matching Fable 5.1) at Opus pricing tier makes agentic coding economical for continuous, multi-hour sessions. For builders: this is the model to default to for any complex agentic workflow starting Sept 22.

HOW TO USE IT

API model string: claude-opus-5-5. Migration from claude-opus-5 is drop-in — same schema, adaptive thinking now always on. Recommended for: multi-hour agentic sessions, large codebases, complex reasoning tasks. For simpler tasks, use Sonnet 5.5 (Sept 28).

claudeopus-5-5releaseanthropicclaude-5-5-family
ORIGINAL SOURCE
https://support.claude.com/en/articles/12138966-release-notes
VIEW ORIGINAL SOURCE →

Top 5 Things to Know About Claude Opus 5.5

  1. 40% cheaper than Opus 5 — $4/$20 per million tokens vs $5/$25 for Opus 5. Genuine cost breakthrough for agentic workloads.

  2. Matches Fable 5.1 on most work — Frontier capability at Opus tier pricing. First time Anthropic has closed the gap this significantly.

  3. Always-on adaptive thinking — No more toggling. Opus 5.5 decides its own reasoning depth per query automatically.

  4. 1M-token context, 128K max output — Same generous limits as Fable 5.1 and Opus 5. Fits large codebases in one call.

  5. Multi-platform day-one — Available on Claude API, Amazon Bedrock, AWS, Google Cloud, and Microsoft Foundry from launch. Enterprise buyers can procure through existing contracts.

How to Migrate from Opus 5 to Opus 5.5

  1. Change model string from claude-opus-5 to claude-opus-5-5 in your API calls
  2. Remove any manual adaptive thinking toggles — it’s always on now
  3. Test on a representative agentic workload — expect similar quality at 40% lower cost
  4. Update billing forecasts to reflect new pricing tier
  5. If using Fable 5.1 for cost reasons, benchmark Opus 5.5 — it may match your quality bar

FAQ

What is Claude Opus 5.5?

Claude Opus 5.5 is Anthropic’s frontier agentic coding model released September 22, 2026. It’s the first model in the Claude 5.5 family, matching Claude Fable 5.1 performance on most workloads at 40% lower cost than Claude Opus 5. Pricing is $4 per million input tokens and $20 per million output tokens.

When was Claude Opus 5.5 released?

Claude Opus 5.5 was released on September 22, 2026. It’s available on the Claude API, Amazon Bedrock, Claude Platform on AWS, Google Cloud, and Microsoft Foundry from day one.

How much does Claude Opus 5.5 cost?

Claude Opus 5.5 costs $4 per million input tokens and $20 per million output tokens. Cache reads are $0.20 per million tokens. This is 40% cheaper than Claude Opus 5 ($5/$25).

Is Claude Opus 5.5 better than Fable 5.1?

Anthropic states Claude Opus 5.5 “performs at the level of Claude Fable 5.1 on most work.” Fable 5.1 remains the top-tier Mythos-class model. Opus 5.5 matches it at lower cost for typical workloads. Fable 5.1 may still edge ahead on the hardest reasoning tasks.

What model string do I use for Claude Opus 5.5?

Use claude-opus-5-5 in API calls. This replaces claude-opus-5 and is a drop-in migration — same request schema, adaptive thinking is now always enabled by default.

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